Hi, Am Sonntag, den 15.09.2013, 16:48 -0400 schrieb Richard Eisenberg:
What was the end result of the discussion on abstraction? Can a library control how its types are coerced?
there is no end result, as this is just a language feature. But the current state of affairs is that: * A newtype can be casted only if its constructor is visible. * Casting below a type constructor (instance Coercible a b => Coercible (Maybe a) (Maybe b)) is possible if the roles allow it; the constructor does not have to be visible or exposed, except that * in Safe Haskell code, the constructor or the typecon (and all constructors of all typecons used in the definition of the typecon) has to be visible. So once you know your syntax for role annotations it would make sense to annotate the arguments of Set and Map (first one only) in base before we release 7.8. Greetings, Joachim PS: Do we have regular builds of master, including users’ guide and haddock, somewhere that I can link to in such a mail? -- Joachim Breitner e-Mail: mail@joachim-breitner.de Homepage: http://www.joachim-breitner.de ICQ#: 74513189 Jabber-ID: nomeata@joachim-breitner.de